2472 Inorganic Chemistry, Vol. 12, No. 10, 19 73 Table I. Rate Constants for the Reaction of Co(II1) Complexes with CO,.- Radicals=
k(CO,.- t complex), M-’sec-’
Complex
X
Co(NH,),X2’
NH, H,Ob OH-C c1NO,- (N bonded) NO,- (0bonded) CH,CO,C,H,CO,C,H, CH, C0,NC,H,CO,- d (0 bonded) NC,H,e (N bonded) p-NCC, H, CO $ p-02NC6H4C0,p - 0 , NC6 H,CH, C0,-
Co(bipy),
,+
1.1 (k0.3) x l o 8 1.7 (i0.3) X l o 8 < 3 ( + i s )x 107 1.5 ( i 0 . 3 ) x lo8 4 ~ 1 )the , observed chemical shift is more than 10 Hz from the free ligand position and increases as the temperature is lowered. This strongly indicates that another exchanging species is present in solution. This conclusion is supported by the fact that at low temperatures (103/T > 4.4) the slope of the line width plot is about twice that expected for a relaxation process controlled by the electron spin relaxation rate.8 It is possible that the behavior of the chemical shift at low temperatures is due to pseudocontact shifts of ligand mole( 1 ) G. Schmauss and H.Sprecker, 2. Anorg. Allg. Chem., 364, 1
( 19 69). (2) N. M. Karayannis, L. L. Pytlewski, and M. M. Labes, Inorg. Chim. Acta, 3,415 (1969). (3) N. M. Karayannis, C. M. Mikulski, M. J. Strocko, I,. L. Pytlewski, and M. M. Labes, J. Inorg. Nucl. Chem., 33, 3185 (1971). (4) N. M. Karayannis, J. V. Minkiewiez, L. L. Pytlewski, and M. M. Labes, Inorg. Chim. Acta, 3, 129 (1969). ( 5 ) M. Ciampolini, Struct. Bonding (Berlin), 6, 5 2 (1969). (6) C. A. L. Becker, D. W. Meek, and T. M. Dunn, J. Phys. Chem., 74, 1568 (1970). (7) T. J. Swift and R. E. Connick,J. Chem. Phys., 37, 307 (1962). (8) R. W. Kluiber, R. Kukla, and W. Dew. Horrocks, Jr., Inorg. Chem., 9, 1319 (1970), and references cited therein.
